Hereto, it has been known that as antibiotics a great variety of cephalosporins having the basic skeleton of the nucleus of the formula(A): ##STR4## have effective antibacterial activities and are widely used as antimicrobial agents for infectious diseases caused by various Gram positive and Gram negative strains.
A variety of cephalosporins whose 7-position has 2-aminothiazolyl acetamino group substituted with .alpha.-oxyimino group have been known. Particularly, the following compounds exhibiting strong antibacterial activities against the enterobacteria have been reported: Cefotaxime in U.S. Pat. Nos. 4,152,432 and 4,098,888; Cefmenoxime in U.S. Pat. 4,098,888 and 4,476,122; Ceftriaxone in U.S. Pat. No. 4,327,210; Ceftazidime in U.S. Pat. Nos. 4,258,041 and 4,329,453.
These compounds, however, show relatively weak antibacterial activities against Staphylococcus when compared with Cephaloridine in French Patent No. 1,384,197 or Cefazoline in U.S. Pat. No. 3,516,997.
Moreover, Ceftazidime exhibits poor antibacterial activity against Staphylococcus, although its antibacterial activity against Pseudomonas is relatively stronger than that of other known cephalosporins.
The present inventors have conducted intensive research to prepare cephalosporins having improved antibacterial activities against Staphylococcus with strong antibacterial activities against Pseudomonas. As a result of prolonged studies on numerous cephalosporins, we found the 3-substituted cephem compounds show superior antibacterial activities against both of Staphylococcus and Pseudomonas.